1. Field of the Invention
The present invention relates to a capacitive sensor, and more particularly, to a method for measuring a velocity of a conductor pressing on a capacitive sensor.
2. Description of the Related Art
In recent years, due to the development of technology, control buttons, such as buttons of an elevator or a game console, evolve from a mechanical type of button into a touch sensor. FIG. 1 is a circuit diagram depicting a capacitive touch sensor in the prior art. Referring to FIG. 1, the touch sensor includes a sensing electrode 101, a resistor 102 and a sensing-control terminal 103, wherein the sensing electrode 101 in the circuit is equivalent to a grounding capacitor Cx.
FIG. 2 illustrates an operational waveform diagram of a node A coupled to the sensing electrode 101 and the resistor 102. Referring to FIGS. 1 and 2, the sensing-control terminal 103 charges the node A to a first preset voltage V20 at the beginning, and then the node A is set to high-impedance. Afterward, since the sensing electrode 101 is equivalent to the grounding capacitor Cx, the sensing electrode 101 starts to discharge through the resistor 102. The sensing-control terminal 103 continuously detects a voltage of node A. When the voltage of node A discharges to a second preset voltage V21, the sensing-control terminal 103 determines whether a finger touches the sensing electrode according to a period when the voltage of node A is discharged from the first preset voltage V20 to the second preset voltage, and then the sensing-control terminal 103 begins to charge the node A.
Referring to FIG. 2, the waveform 201 is a voltage waveform of node A when the finger does not touch the sensing electrode 101, and the waveform 202 is a voltage waveform of node A when the finger touches the sensing electrode 101. According to the waveforms, when the finger touches the sensing electrode 101, the equivalent capacitor of the sensing electrode 101 is increased so that a discharge time T2 of the waveform 202 is longer than a discharge time T1 of the waveform 201. Therefore, as long as it is determined that the period when the voltage of node A is discharged from the first preset voltage V20 to the second preset voltage V21 is longer than the discharge time T1 by the sensing-control terminal, it can be determined that the sensing electrode 101 is touched.
However, the conventional capacitive sensor is only applied to the application of detecting whether the sensor is connected with a conductor. The capacitive sensor does not have any other application in the prior art. Due to the development of the industry of the game console, manufacturers have started to find novel game-playing ways and easy operation methods for the game console. Thus, a control method based on the capacitive sensor is provided in the present invention.